Water Oxidation by a Copper(II) Complex with 6,6′-Dihydroxy-2,2′-Bipyridine Ligand: Challenges and an Alternative Mechanism

Abstract

Recently, copper(II) complexes have been extensively investigated as oxygen-evolution reaction (OER) catalysts through a water-oxidation reaction. Herein, new findings regarding OER in the presence of a Cu(II) complex with 6,6′-dihydroxy-2,2′bipyridine ligand are reported. Using scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, Raman spectroscopy, in situ visible microscopy, in situ visible spectroelectrochemistry, X-ray absorption spectroscopy, and electrochemistry, it is hypothesized that the film formed on the electrode's surface in the presence of this complex causes an appropriated matrix to produce Cu (hydr)oxide. The resulting Cu (hydr)oxide could be a candidate for OER catalysis. The formed film could form Cu (hydr)oxide and stabilize it. Thus, OER activity increases in the presence of this complex.

Synthesis of chiral Cu(II) complexes from pro-chiral Schiff base ligand and investigation of their catalytic activity in the asymmetric synthesis of 1,2,3-triazoles

“…Similar to 1 , the Cu(II) ion is five coordinated in 2 and the CuN 2 OBr 2 coordination environment has distorted square pyramidal geometry with τ = 0.064. The Cu–N and Cu–O bond lengths in the equatorial positions of 2 are close to the similar bonds in 1 (see Table 2 ) and are in the normal range reported in similar Cu(II) complexes 68 – 71 . The Cu–Br1 and Cu–Br2 bond lengths are 2.3602(10) and 2.6607(10) Å, respectively and confirm their coordination to equatorial and axial positions and the presence of Jahn–Teller distortion in the axial direction.…”

Oxygen-Evolution Reaction Promoted by Iron and Brass Under Alkaline Conditions

“…Visible diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to characterize the optical properties of solid materials. 8,9 Measuring the diffuse reflectance of a sample across a range of wavelengths in the ultraviolet and visible regions of the electromagnetic spectrum provides information about the electronic structure and composition of the material. 8,9 This technique is particularly valuable in studying pigments, catalysts, semiconductors, and other materials where traditional transmission-based spectroscopy may not be feasible.…”

2-Pyridonates: a versatile ligand platform in 3d transition metal coordination chemistry and catalysis

“…79 An alternative mechanism via Cu-complex decomposition and formation of a Cu thin film on the electrode was also proposed. 80 Papish and coworkers showed that reaction of CuSO 4 with 6,6′-dihydroxy-2,2′-bipyridine in ethylene glycol led to the formation of the well-defined Cu[N] 4 complex 32a that occurs in different protonation states depending on pH (Scheme 12, top). 81 Complexes 32 displayed moderate activity in the electrocatalytic water oxidation at even lower overpotential (447 mV) than the related postulated 1 : 1 adduct 31 .…”